Once a consumer dismisses a smartphone alert, it’s gone.

Unless, of course, the brand is like Neiman Marcus and has an in-app message center that can house all of the alerts.

Luxury retailer The Neiman Marcus Group Inc., No. 101 in Internet Retailer’s 2016 Mobile 500, has had an in-app message inbox since it launched its app in 2014.

The inbox lives in the app and contains promotional and editorial messages meant to bring shoppers into specific areas of the app, says Aja Friday, online and mobile marketing manager at Neiman Marcus. Messages, which are sometimes sent as smartphone alerts, include special event invitations, promotions and automated shipping alerts.

“Not every inbox message has a corresponding push notification, but all push notifications have a corresponding inbox message,” Friday says. A push notification is an alert sent to the smartphone lock screen of a consumer who has the retailer’s app and has agreed to receive such messages.

When a consumer receives an alert on her smartphone from the Neiman Marcus app, she can tap on it to open the app’s message center and display messages containing more information, or she can dismiss the alert. Either way, the message will remain in the app’s inbox so she can review it at any time.

When Neiman Marcus has a new message for the inbox not sent as a push notification, an icon will show up on the app located on her smartphone’s home screen. The icon will display the number of unread messages in the shopper’s inbox. Neiman Marcus’ app message center increases app opens and app sales, Friday says, without providing specifics. Plus, having the inbox allows Neiman Marcus to reach a larger audience, because not all consumers opt-in to receive smartphone alerts, she says.

The retailer sends one to three in-app messages in a typical week, but sometimes sends more, Friday says. Friday would not disclose how many of those messages  it sends as push notifications.

“Neiman Marcus leverages push notifications when the content or message warrants it,” Friday says. “We can target and use them in a way that is relevant and respectful to the customer without being too interruptive.”

Smartphone alerts are meant to drive app opens, which they do, Friday says. “We see increased app opens whenever we send a push notification,” Friday says.

The retailer is also experimenting with sending push notifications that are relevant to consumers who live in a certain geographic location. Neiman Marcus is using its in-store beacon pilot to help with location-based targeting. Beacons are small wireless transmitters that can sense a smartphone’s location via Bluetooth low energy. Beacons can send push notifications to consumers who have the retailer’s app.

“We are constantly testing, especially in looking at ways to enhance the in-store experience,” Friday says. “With our recent launch of geo-targeted push notifications and inbox messages, we have seen open rates increase between two and three times versus non-geo-targeted notifications and messages,” she adds.

For retailers wanting to integrate a message center into their app, mobile app developer Urban Airship—which developed Neiman Marcus’ in-app message center—estimates it takes between four and six weeks of a developer’s time.

Neiman Marcus only has an iPhone app. In the 2016 Mobile 500, Internet Retailer estimates Neiman Marcus’ mobile sales at $154 million, 25% of which are from its app.